Purge system for refrigerative circuits



Ju'ne 15, 1943. w. E. ZIEBER PURGE SYSTEM FOR REFRIGERATIVE-CIRCUITS 2Sheets-Sheet- 1 Filed Aug. 8. 1941 QN A Noimongm Isdn uuMnl Zmventordowwmmuoo Gttcrnegs June 15, 1943. l w. E. zlEBER PURGE SYSTEMAFORREFRIGERATI'VE CIRCUITS Filed Aug. 8', 1941 2 sheets-sheet 2 E. w23 n50:

. xdUW ZUB ZOU A ahw) nnentor Patented June 15,

PURGE SYSTEM FOB REFRIGERATIVE CIRCUITS l William E. Ziebcr, York, Pa.,assignor to York Ice Machinery Corporation, York, Pa., a corporation ofDelaware f Application August 8,1941, serial No. 406,061

' (c1. sz-115)' 13 Claims.

This invention relates to refrigeration and particularly to purgingsystems for use with refrigerative circuits. While the invention can bearranged for manual control, a feature is the pro-v vision of automaticmeans which render manual control unnecessary and which respond tocondiv tions within the system indicating the need of the purgingoperation.

The invention is of marked 'utility in connec- I tion with refrigerantsof the Freon class and generally with refrigerants with whichlubricating oil is freely miscible, particularly .those in which themiscibility is vcharacteristic of all degrees of oil concentration.Wherethis is the case, gravity separation of the lubricant from therefrigerant is impracticable so that special provision must be made forthe desired separation. Refrigerants having this character ofmiscibility with the oil are typified by the Freon group and thediscussion will be based on the use of Freon simply as examples andwithout implying any necessary limitation to this particular field.Freon is a trade name, and various types of the general class areVdistinguished by numbers as F-11,F12,etc.

The invention is useful in any refrigerating plant in which theevaporator, or both evaporator and condenser operate below atmosphericpressureand hence are subject to in-leakage of air and water vaporduring normal operating periods. Leakage, of course, is not a normalfunction but it cannot always be prevented. In an air conditioningsystem, to take one familiar example, the evaporator is commonlyoperated at the circuit as completely as is reasonably practicable.

With certain refrigerants commonly used in air conditioning theoperating pressure ranges are rather low so that there is a tendency foratmosatmospheric air always contains some water vapor, the entrance ofair is attended with the entrance of water in the vapor phase. Theoperation of most compressors is such as to cause mix- The inventionprovides for the segregation of V elimination of the oil separator.

y pheric air to enter the refrigerative circuit. Since ture of somelubricating oil with the refrigerant.

such oil from 'the refrigerant. vThe segregation of the oilis automaticbut its removal from the circuit is preferably under manual control.

The operation cf the purging system for separating and rejecting the airis fully automatic. The separation of the water is automatic, thequantity is not great enough to render automatic discharge worth theextra complication.

To embodiments of the invention are shown, one involving the use of asmall secondary reciprocating compressor to withdraw refrigerant, airand water vapor from the condenser and deliver them to a secondarycondenser, and the other involving the use of a secondary condensingcoil operated at a temperature so low as to make the use of a compressorunnecessary. Such a low temperature condensingcoil forming part of thepurge device is peculiarly desirable in plants.,

where a low temperature cooling liquid or a low temperature refrigerantis rendered available by extraneous meansl because low temperaturepermits eicient purging. Elimination of the secondary compressor, inplants in which the main compressor is of the centrifugal type, permitsReciprocating compressors are likely to contaminate the refrigerant withoil and their elimination reduces the oil problem practically to thevanishing point.

' Two types of automatic control for the purgel device are disclosed,and either may be used with either of the two embodiments justmentioned. These two controls are characterized, one by a rather widecontrol range which ordinarily gives sufliciently precise control, andthe other by a very narrow control range, which is required in caseswhere temperature and pressure in the main condenser are rather. l'owand condensation of water vapor in the condenser may occur unless aprecise purge control is afforded. Low condenser temperatures areencountered in known types of circuit in which cascade cooling is used,i. e., cooling of the .main condenser by an auxiliary refrigeratingcircuit.

Generally stated, according to the invention, av

mixture of refrigerant vapor, water vapor and air is drawn from Athemain condenser and delivered to a secondary purging 'condenser which isoperated at a lower temperature than the main condenser. If thistemperature is suiliciently low, no secondary compressor is neede'd, butin most cases, it is desirable to use a compressor towithdrawrefrigerant vapor with air and water vapor from the main condenser anddeliver them under oiftake.

elevated pressure to the secondary condenser. In thisv secondary orpurge condenser, the refriger- V ant isliquefied almost completely sothat the sures) to` liquefy all of the refrigerant. Theliquefiedrefrigerant is returned to the system after a gravity separation ofWater therefrom, and on its way back to the system may be fed throughthe evaporative cooling coil of the secondary or purge condenser. Inthis condenser the oil is deposited and flows to a bailied oil-separatorwhich may be drained from time to time. The vaporous refrigerant, thusfreed of air, water and oil returns to the low side of the main circuit.

The automatic control puts the purge circuit into operation whenever airis present in the condenser in excess of a chosen proportion When thepurge device operates, air mixed with a minimum quantity of refrigerantis discharged from the circuit. All water is separated from the liquidrefrigerant and discharged. The refrigerant (includingl if desired, somedrawn from the main condenser) is freed of oil and returned to the lowpressure side of the main refrigerative circuit. As stated, except fordraining off of the oil and of the Water, each of which is required atrelatively long intervals, the operation of the system is completelyautomatic.

Preferred embodiments of the invention will now be described byreference to the accompanying drawings.

In the drawings:

Fig. 1 is a diagram, partly in section, showing the embodiment using asecondary compressor, and a controller ofthe differential pressure type.

Fig. 2 is a section on the line 2-2 of Fig. 1.

Fig. 3 is a fragmentary view of the Weir notch through which the liquidrefrigerant flows.

Fig. 4 is a sectional view of a protective valve used on the air ventline. l

Fig. 5 is a fragmentary view of the local c ooler associated with thepurge offtake from the Vconcompressor is omitted.

Embodiment of Figs. 1-5

The main refrigerative circuit comprises an evaporator II Aof any type,a compressor I2 of any type (but here assumed to be of the centrifugaltype), drawing vaporous refrigerant from evaporator I I and deliveringit at higher pressure to condenser I3 which ordinarily would be of theWater-cooled shell and tube type. Any cooling medium can be used in thecondenser.

Refrigerant liquefied in the condenser collects in the receiver f4 fromAwhich itis fed to the evaporator II by any suitable controlling mea'nsconventionally indicated at `I 0.

Communicating freely with the vapor space in condenser I3 by port I5 isa cooled purge-oiftake chamber I6 (see Fig. 5). This is cooled by anymeans such as coil I1 through which a cooling uid is circulated. Thepurpose is to cool chamber I6 below condensing temperature and thusstimulate a free flow of non-condensable gases (chiefly air) to thechamber and thence to the The cooling fluid may, for example,'be

condenser cooling water on'its way to the main water spaces of thecondenser I3, and hence cooler than the condenser, but this is a matterof detail.

The purge oitake line I0 leads from chamber I 6 to the intake ofsecondary compressor I9 which discharges through check valve 2| andair-cooled condenser 22 to the purge drum 23 in which is mounted thesecondary condensing coil 24. The condenser 22 is :merely an economlzerand may be omitted. The check valve 2I is important because itpreventsreflux of water to the compressor I9 when the latter stops. Thiswater has been found to have serious corrosive action upon' thecompressor if allowed to flow back to the compressor when. the latterstops, To thesame end the pipe connections from check va1ve'2l to 'purgedrum 23 are made small so that high ow rates (say 1,000 ft. per minuteor more) are had, the purpose being to sweep water droplets toward drum23 and prevent retention of slugs of water in the piping.

Coil 24 is fed with liquid refrigerant and oper- `ates at substantiallythe pressure and temperature of evaporator il, as will later appear. Itcondenses the major portion of the refrigerant entering drum 23. The airand a small amount of uncondensed refrigerant discharges through theloaded relief valve 25 which controls air vent pipe 25.

The relief valve 25 can be used alone, but because such valves sometimesfail to seat tightly,

, a protection valve 21 is interposed between drum 23 and valve 25. Thestructure of the protection valve is shown in Fig. 4, and since thevalve is of known mechanical construction (but heretofore used for awholly different purpose) only a brief description is needed.

The valve proper 28 opens in the direction of flow toward valve 25. Itis loaded in a closing direction by coil compression spring 29. The

y spring loading is opposed by pressure in drum 23 communicated throughtube 3l to bellows 32,

' causing the bellows to react in a. valve opening direction on stem 33which engages the valve 28. Bellows 34 form a packless seal for stem 33.The loading of spring 29 isv adjustable and is so set that the valve 28closes except when purging pressures exist in drum 23, at which time itopens and transfers vent control to the loaded vent valve 25. Yalve 2will close tightly at other times. 'Hence valve 25 will not weepcontinuously even though its seat should become scored.

The valve 25 is simply a spring loaded relief valve set to open whenchamber 23 is at purging pressure, and by purging pressure is meant'apressure substantially higher than the pressure corresponding to thetemperature of the coil 24 as determined by the thermo-dynamicproperties of the refrigerant used in circuit I I, I2, I3, I4.

This can be illustrated by a practical example.

VAssume that the refrigerant is F-11 and that the evaporator II operatesto cool water to 40 F.

The evaporator II would operate at a, pressure of about 6 lbs. per sq.in. absolute and the condenser would operate at about 10 lbs. gage,assuming cooling water at about F. With the connections as shown inFigure 1, the refrigerant is slightly below the bottom of notch di.

through the valve 25, which is adjusted to open only in the relativelyhigh pressure range above suggested.

Refrigerant liquefied in drum 23 passes by dip pipe 35 to the gravityseparation chamber 36, shown formed as a downward extension of drum 23.The entire structure is insulated to minimize the entrance of heat, suchinsulation being indicated at 30. The arrangement of chamber 38 will beclear from a consideration of Figs. -`1, 2

and 3.

There is a water overow weir comprising a weir notch 31 in partition 38controlling now to water collecting sump 39. There is a refrigerantoverilow weir comprising a weir notch 4| in partition 42 controllingilow to refrigerant collect chamber 63. y

Since the refrigerant isassumed te have a higher specic gravity thanwater, the notch 3l is slightly higher than notch dl. To facilitategravity separation in chamber 88 at least one vertical cross bame dd isused. Two bales are shown and their function is to suppress turbulencecaused by the entrance of liquid through dip pipe 35. The bottom edge oibame dt is above the bottom of chamber 36 and the top edge Thus notch 3lskims water ofi'. The rate of horizontal liquid now in chamber 36 shouldbe low, say six to twelve inches per minute. Refrigerant, thus freed ofWater, passes below a dip partition t5 to reach weir notch di. Anyfreely miscible oil would travel with the refrigerant.

Water is drained away from sump 39 by manually opening valve dt. li'loatcontrol of valve S8 woyld be an unnecessary complication since theamount of water to be discharged is small. However', the discharge fromchamber d3 is iloat controlled, the drain line di leading to a high sidefloat valve t8. A' pressure equalizing connection 49 to the vapor spacein purge drum 23 is pro,

vided. A oat valve similar to t8 could replace valve d6, and such asubstitution would involve only mechanical skill. v

Refrigerant passing through valve It is led by line 5I to the entrance(upper) end of coil 28 which is carefully designed to drain all oilprecipitated therein to its lower discharge end. This oil might, forexample, enter the system at the reciprocating secondary compressor I9.The system. need not withdraw oil with refrigerant from condenser I3where compressor i2 is of the centrifugal type, since contamination ofrefrigerant by oil does not occur to any appreciable extent in suchcompressors. However, if the main compressor is of the reciprocatingtype some of the oil which might then become mixed with refrigerantwould pass from condenser I3 through expansion valve 52, about to bedescribed, and

' would be separated by the oil separator 5l.

Snce the refrigerant passing" valve d8 is insuiilcient to supply thedemands of coil 2d, an automatic expansion valve 52 of the superheatcontrol type is interposed in a connection 58 between leaving the coiland affecting the temperature of bulb 34 will be slightly superheated. l

Refrigerant leaving coil 28 and oil draining therefrom pass byconnection 56 to one end of oil separator drum 51 which has ballles 58for arresting oil droplets and a manually operable normally closedoildrain valve 58. 'I'he other end of the drum is connected by line 6I withevaporator Il, i. e., to the low side of the main refrigerating circuit.As stated, the system can operate to` the invention provides forrecovery of some but not all of the oil entering the main condenser.Since the valve 52 isalways eiiective to feed coil 24, some oilseparation is occurring from time to time irrespective of the cycling ofthe purge device as long as the main compresser operates.

The purging circuit above set forth is active only when conditions inthe condenser are such as to require purging. This is evidenced by riseof condenser pressure unduly above the pressure corresponding to thetemperature of liquid refrigerant in the condenser. At such times thecompresser I9 is operated. At all other times the compressor isinactive.

Compressor I8 is driven by electric motor t2 which receives current fromlines 63, $8 through normally closed switch 65. A control switch 68operated by opposed bellows motors 6l, 68 reacting upon lever 89 whichis iulcrumed at 'II starts and stops motor' 62 according to conditionsin condenser i3. Bellows motor 6l which acts in a switch closingdirection is subject to pressure in the vapor space in condenser I3.Bellows mot/or 88 which acts in a switch opening direction is connectedwith a thermostatic bulb 'I2 submerged in liquid refrigerant incondenser I3 and containing a volatile liquid, conveniently of the samecomposition as the liquid refrigerant, so as to have identical thermalcharacteristics. A spring I3 gives a moderate opening bias to theswitch.

Such a switch will run motor 62 and compressor I9 whenever condenserpressure is out of ,line with the'temperature at which the condenser isoperating. 'I'he device cannot; be arranged for very precise control butis commercially satisfac tory.

Precise control, Fig. 6

When comparatively precise control is desired, the control mechanismillustrated in Figure 6 is used in lieu of the parts 88 to I3 inclusive.In Figure 6 only suilcient mechanism is'illustrated to make clear howthe precise control mechanism is substituted, and parts which areidentical with parts in Figure 1 are given the same reference numeralsused in Figure 1 but with the distinguishing letter a.

erant to coil 2t at rates such that refrigerant 75 A loadedfvalve 8| isinterposed between line I8a which is the suction line to the secondarycompressor, and the chamber [6a which is in free communication with thevapor space in the condenser I3a by way of the non-restricting openingl5a. The valve 8| is adjusted to produce a small pressure drop betweenthe chamber Ita and the suction line I8a, the purpose being to ensurethat when the secondary compressor is running the suction line I8a willbe maintained at a pressure below the pressure in the condenser I3a.

A drum 82 is -in free communication with the chamber Ilia by way of thepipe 83. It is important that this pipe be large enough to permit freeflow. The drum 82 is also connected at its bottom with the liquid spacein the condenser |3a by way of the pipe 84. 'I'he drum 82 is inrestricted communication with ,the suction line I8a by way of the choke85 scr that when the secondary compressor runs there is retarded flowfrom the drum 82tot trie suction line I8a.

In the drum 8,2 isis:refrigerating surface or coil 88 which must @beoperated at a temperature below, usually atleast to 25 degrees below,the lowest temperature which is ever maintained-in the condenser |3a. Itis convenient to refrigerate this coil by evaporating liquid refrigerantin the coil, but cold water or brine may be circulated through it.

Details of the supply and return connections to the coil 86 are notillustrated because they would be conventional in any event and are sub-A ject to wide variation.

A thermostatic switch of the insertion type is illustrated at 81. Thethermally responsive element extends axially through the chamber 82 soas to be subject to the temperature of gaseous medium in that chamber.'I'he thermostatic switch 81 is adjusted to close on fall of temperatureto a value below temperature in condenser |3a and preferably'only a fewdegrees above the temperature at which the coil 86 is maintained. Thethermostatic switch 81 controls the motor 62a which is the driving motorof the secondary compressor.

Assume now that the motor 62a and the secondary compressor driventhereby are not running. Because the coil 86 is at a lower temper-,ature than the condenser |3a, vaporous refrigerant will enter freelythrough the pipe 83, c ondense in the drum 82 and drain through the pipe84. Whatever the temperature of thel coil 88 may be, refrigerant wouldenter and condense at a rate suiilcient to absorb the entirerefrigerating effect of the coil. Thus the temperature of gaseous mediain drum 82 is that corresponding to the pressure in condenser |3a andnothing happens so long as no air is present. If air be present in thecondenser |3a it will enter the drum 82 with the vaporous refrigerantand will accumulate in that drum. Ulti- :mately the concentration of airwill become such lthat little vapcrous refrigerant can enter, conldensation `of refrigerant in drum 82 is reduced, and the coil 86 becomeseffective to reduce the temperature of the gaseous media in drum 82.v

This fall of temperature ultimately causes thermostatic switch 81 tostart the motor 62a.

When this happens the secondary compressor will draw vaporousrefrigerant and air in substantial quantity through the valve 8| and inlimited quantity through the choke 85.

The flow capacity of choke 85, the pressure differential imposed by thevalve 8|, and the volume of the chamber 82 are so coordinated that thechamber 82 will not be too rapidly swept free of air. If the secondarycompressor could draw freely from the drum 82 this drum would be quicklyfreed of air and the motor 62a would promptly be shut down by thethermostatic switch.

Modified embodiment, Fig. 7

In this ligure the control of Figure 6 is shown. Parts identical 'withFigures land 6 aregiven the same identifying numeral with the letter b.

Tooperate such a system there must be some means (cold brine or volatilerefrigerant) for cooling the coil 24h to a sufficiently low temperatureto ensure eilicient operation. The secondary compressor |9 is omittedbecause low temperature implies low pressure in drum 23h. Connection |8bleads directly to purge drum- 2 3bto which flow occurs because the drumis always below condenser pressure.

An electrically operated valve 9| of limited flow capacity controls thisconnection, is normally closed and opens when winding 93 is excited. Theiiow of cooling medium through coil 2lb is desirably (but notnecessarily) controlled by a similar electrically operated valve 92which is normally closed and opens when winding 94 is excited. Anadjustable by-pass 90 permits limited flow past valve 92 when the latteris closed so that coil 24h is never completely inactive. The reductionvof flow through coil 2lb is simply in the interests of economy.Thermostatic switch 81h closes the circuit through windings 93, 94 whentemperature in drum 82h falls below a chosen value. The importa'ntfunction is that valve 9| (and valve 92, if used) shall open whenpurging is needed, i. e., when temperature in drum 82h falls below achosen Value.

An important relationship is that the total condensing capacity of coil2lb when valve 92 is open shall exceed the flow capacity by way of thevalve 9|, so that coil 24h when active will cause a decided pressuredrop in drum 23h.

The arrangement described is simply a convenient one of several whichmight be devised by persons skilled in the art to secure the desiredresult. 'I'he control used in Figure 1 is obviously adaptable.

As in the device of Figure 6, valve 8| b is set for a moderate pressureldrop between condenser |31) and line |8b, andits setting is coordinatedwith the volume of chamber 82h and iiow capacity vof choke 85h to ensureproperly sustained purging.

Float valve 48h delivers recovered refrigerant directly to evaporatorIIb in the preferred arrangement, illustrated. This is practicable fortwo reasons; the coil 24h is here illustrated as cooled `by extraneousmeans, so the refrigerant need not be fed to that. No oil separator drumsuch as the part 51 of Figure l is'here required in view of the omissionof the secondary compressor, and the assumed use of a main compressor ofthe centrifugal type.

Consideration of Figure 7 will indicate that the resistance of the backpressure valve 8|b, the now resistance through connection |8b and valve9| and the pressure range required for operation of the valves 2lb and25h impose the requirement that the valve 25hl must open at some presitis ldesirable that the coil 2lb operate at a lcw temperature.

To assume a practical example and without yimplying any limitation tothe values stated, itv

will be assumed that the condenser IIb is operated at lbs. per sq. in.gage and the purge valve h opens at approximately 2 lbs. gage. The coil24h at whatever low temperature it is operated, should have a condensing'capacity so related to the ow capacity of valve 8| for vaporousrefrigerant thatin the absence Vof air in drum 23h a pressure will beestablished in the purge drum 23h lower than the opening pressure ofvalve 25h, here assumed to be 2 lbs. gage.

Under these conditions if air is present in the condenser |312 andcauses the mechanism in the drum 82h to open the valves 9| and 92, airwill accumulate in the purge drum 23h. Thus pressure which wouldinitially be below the setting of the valve 25h would gradually risewith the increasing concentration of air and the consequently reducedcondensing effect of coil 2th until the valve 25h would open. Thisopening would occur only when the`air concentration in the drum 23h isconsiderable. As a practical matter, the opening of the valve 25h isintermittent, the opening of the valve serving to reduce the airconcentration and its resulting closure initiating a new increase-ofconcentration.

General considerations The valve 2-5 in the arrangement of Fig. 1 willalso open and close for similar reasons at times. When the compressor I9starts the air concentration will -be high and valve 25 may remain opencontinuously for a considerable period but in time, and .beforecompressor I9 shuts down, the air concentration will have been reducedso that valve 25 will close and open. alternately, the openl periodstending to become shorter .because the rate of delivery of air to drum23 diminlshes.

Both the embodiments of Figs. l and '7 have the word "air being used ina loose sense as .typif'ying any non-condensable gas or mixture ofnon-condensable gases which might be present in the refrigerativecircuit, and the claims should be interpreted on this understanding.

What is claimed is:

1. The combination of a refrigerative circuit containing a volatilerefrigerant and including a condenser; a purge drum; a loaded ventvalvecontrolling flow fromy said drum and set to openwhen pressure in thedrum exceeds a definite value; refrlgerative means serving to cool gasesin said drum to a temperature which for said refrigerant issubstantially lower than that.corre. spending to said pressure; meansfor returning condensed refrigerant from said drum to said circuit;means for delivering from the'condenser to the drum, at a pressurehigher than the setting' of said vent valve, vaporous refrigerant', andair when air is present in the condenser; and a controller responsive tothe presence of air in the condenser and including a thermallyresponsive element, said controller serving to control the last namedmeans.

2. The combination of a refrigerative circuit containing a volatilerefrigerant and including a condenser; a purge drum; a loaded vent valvecontrolling flow from said drum and set to open when pressure in thedrum. exceeds a denite in said drum to a temperature which forsaidrefrigerant is substantially lower than that cor.

responding to said pressure; means for returning condensed refrigerantfrom said drum to said circuit; means for delivering from the condenserto the drum, at a pressure higher than the setting of said vent Valve,vaporous refrigerant, and air when air is present in the condenser; andmeans responsive to pressure-temperature relations in thecondenserserving to control the last named means.

3. The combination of a refrigerative circuit containing a. volatilerefrigerant and including a condenser; a purge drum; a loaded vent valvecontrolling ow from said drum and set to open when pressure in the drumexceeds a definite value; refrigerative means serving to cool gases incommon the idea of controllable purging circuits in response tocondenser conditions, and the incorporation in the purge circuit ofcooling means and a pressure operated purge valve which coact to ensurepurging now at times when the air is present to the practicable maximumand Vaporcus refrigerant is present only to the practicable minimum inthe mixture in drum 23h.

Two embodiments of the purge circuit and two specifically differentcontrol mechanisms have been described, with the idea of illustratingthe in said drum to a temperature which for said refrigerant issubstantially lower than that corresponding to said pressure means forreturning condensed refrigerant from said drum to said gcircuit; meansfor delivering from the condenser non-condensable gases. In mostcircuits, air will 1 cication and in certain of the claims as typifyingthe non-condensable gas to be purged.

The invention is not limited to purging air and the claims are notintended to be limited to'air,

to the drum, at a pressure -higher than the setting of said vent valve,vaporous refrigerant, and air" when air is present in the condenser; andmeans for creating a vapor-air atmosphere substantially at condenserpressure and in which the air is concentrated by flow from the condenserand condensation of refrigerant 4vapor therefrom; and temperatureresponsive means in said atmosphere -and connected to control saiddelivering means.

a.v The combination deined in claim' 1 in which the delivering meanscomprises va motor drivencompressor controlled by said controller andhaving its suction connected with the'vapor space of the condenser andits discharge connected with the purge drum, and the loaded vent valveis set to maintain the purge drum at a pressure higher than that in thecondenser.

5. The combination defined in claim 1 in which the delivering meanscomprises a motor actuated valve of restricted flow capacity controlledby said controller and interposed between the condenser and the purgedrum.' and the refrigerative means operate at a temperature so low Ithatthe purge valve is set to open at a pressure lower than condenserpressure.

6. The combination of a refrigerative circuit containing a volatilerefrigerant and including a condenser; a purge drum; a. loaded ventvalve controlling flow from said drum and set to open when pressure inthe drum exceeds a definite value; refrigerative means serving to coolgases in said drum to a temperature which for said refrigerant issubstantially lower than that corresponding to said pressure; aconnection for returning condensed refrigerant from said drumcontrolling flow from said drum and set to open whenA pressure in thedrum exceeds a definite value; refrigerative means serving to cool gasesin said drum to a temperature which for said refrigerant issubstantially lower than that corresponding to said pressure; aconnection for returning condensed refrigerant from said drum to saidcircuit; a water separator of the gravity type in said connection; anevaporator also in said' connection beyond said Water separator, and inwhich refrigerant is evaporated and oil, if present is trapped; andmeans for deliveringA from the condenser to the drum, at a pressurehigher than the setting of said vent valve, vaporous refrigerant, andair when air is present in the condenser.

8. The combination cfa refrigerative circuit containing a. volatilerefrigerant and including `a condenser; a purge drum; a pressureoperated vent valve controlling purging flow from said drum and arrangedto open when pressure in the drum exceeds a chosen pressure;refrigeratlng means for cooling gaseous media in said purge drum totemperatures materially below that corresponding tosaid chosen pressureon the basis of the thermo-dynamic properties of said refrigerant; meansfor causing vaporous refrigerant, together with water vapor andnon-condensable gases when present, to iiow from said condenser to saiddrum; means responsive to the presence densed in the purge drum.

10. The combination of a refrigerative circuit containing a volatilerefrigerant and including a condenser; a purge drum; a pressure operatedvent valve controlling purging flow from said drum and arranged to openwhen pressure in the drum exceeds a chosen pressure; refrigerating meansfor cooling gaseous media in said purge drum to temperatures materiallybelow vthat corresponding to said chosen pressure on the basis of thethermo-dynamic properties of said refrigerant; means for causingvaporous refrigerant, together with water vapor and. noncondensablegases when present, to flow from said condenser to said drum; meansresponsive to the presence of non-condensable gases in said circuit tocontrol the last named means; means for separating condensed Water fromcondensed refrigerant and withdrawing them separately from said drum,lubricating oil when present from any source iiowing from saidseparating meanswith the condensed refrigerant,- and means for returningsuch condensed'refrigerant to said circuit, said means including anevaporative separatorI in which the refrigerant is evaporated and thetrapped. s

'11.' 'I'he combination of a refrigerative circuit containing a volatilerefrigerant and including a condenser; an air-concentrating chamber infree communication with the condenser; means for cooling said chamber toa temperature lower than' condensing temperature whereby a tendencytoward concentration of non-condensable gases in said chamber iscreated; a ,purge device of the reirigerative separator type; and meansresponsive to the presence of air in the condenser for connecting saidair concentrating chamber to said purge device.

12. The combination of arefrigerative circuit containing a volatilerefrigerant and including a condenser; a chamber having connectionsaffording free entrance of gases and vapors from the condenser and freedrainage of liquid back to thecondenser; means for cooling the interiorof said chamber to a temperature substantially below condensingtemperature; purging means arranged yto draw vapors and gases from saidcondenser and simultaneously to draw them from said chamber at arestricted rate; and a thermostatic controller for said purging meanssubject to temperature of vaporous and gaseous media in said chamber.

13. The combination of a refrigerative circuit containing avolatilevrefrigerant and including a condenser; a purge drum: meansforming a re` stricted communication between the condenser and the purgedrum; a pressure responsive purge valve controlling flow from said drumand ar,- ranged to open at a purge drum pressure lower than condenserpressure; a cooling coil in said drum and operated at a temperaturewhich for the refrigerant in the-circuit is decidedly lower than that4corresponding to the pressure at which the purge valve opens, said coilhaving condensing capacity at least sufficient to condense all therefrigerant that can flow to the purge drum through said restrictedcommunication, a valve controlling. said restricted communication; andmeans sensitive to the presence of non-condensable gases in said circuitconnected to said valve to actuate the same and arranged to opensaidvalve when non-condensible gases are present in substantial quantity andclose it at other times.

WILLIAM E. ZIEBER.

oil so freed from refrigerant is

